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In Dirk Dusharme’s First Word in the April 2006 issue of Quality Digest, he sneaks into the back of the “Church of the Six Sigma” and cannily reports the goings on. In this column, I will burst in through the doors dressed in motley and try to pry the scales off of your eyes, chanting, “DMAIC will set you free!” Do I do this for my own ego?

No.

Well, maybe.

No, no, no, not really. I do this because there really is something beneficial in what we refer to as Six Sigma, but in the absence of a clarifying, or at least dissenting, voice, someone’s momentary reaction becomes petrified into law. This iterative search for the truth could be called the scientific method, or as author and scientist David Brin calls it, CITOKATE (criticism is the only known antidote to error). We love to be right—it’s our favorite drug and we pursue being right in the face of great evidence to the contrary. Usually, the last person to notice that a hypothesis has failed is its originator. Only by testing our premises can we become more certain they are true. In the absence of this, unproven assumptions turn into rules, which turn easily into a faith that has less and less connection to reality.

This means that I may call your (and, gasp, my) premises into question. Are you a scientist who can take a step back and assess your premises—as I think you are—or are you a Six Sigma faith-based indignation junkie playing with matches next to that big stake set up in the town square amidst the firewood? Disagree with me, reason with me, but question and think about what I have to say. Whatever you do, don’t just believe me.

So, in the best tradition of Six Sigma let’s define what in the world we are talking about.

What is Six Sigma? Ask this question of four quality practitioners and you’ll get four different answers and a fistfight. Read four books on Six Sigma and you get three and a half different answers that take up 15 pages each. Ask four business owners who are considering implementing Six Sigma and you get six different answers and a lot of mumbling.

Why is such a popular business initiative so hard to define? Could it be that the professional class—a.k.a. “priests”—of Six Sigma practitioners benefits from a little murkiness? (full disclosure: I consult and teach in the Six Sigma arena.)

The easy answer is that Six Sigma is all about marketing. It’s alliterative, and the first word sounds sexy. (At least I mistype it that way, don’t you? Oh, maybe it’s just me.) It might be that the term Six Sigma has no operational definition at all—it’s a term of convenience that means whatever the person selling or, more importantly, the person buying thinks it means.

I can just hear it now: “Don’t worry your pretty little head about all this confusing terminology. Here are four more TLAs (three-letter acronyms) you can memorize. Won’t that be nice? Just remember, Six Sigma is the cure for whatever ails you.”

Does this remind anyone else of snake oil cures? Should there be a disclaimer on a Six Sigma implementation?—“Warning! The statements your consultants will make have not been verified by the Food and Drug Administration and are not intended to cure your, or any, particular problem.” If Six Sigma is whatever we want it to be, it can never be wrong or inapplicable, and we can always charge for it . . . er . . . use it. If we continue down this path, Six Sigma will become a meaningless fad, and the scientific method, data analysis and expert problem solvers will be tarred with the same brush.

I used to define Six Sigma as, “Anything you need to do to profitably achieve high-conformance, low variability products or services to meet and exceed the needs of your customers.” Forgive me, fellow heretics. I had good intentions.

I was trying to say that Six Sigma fails if all you do is train Black Belts, even if you train them well. They need an infrastructure to to support them, including a linkage between the business’s strategic plan and the projects that you assign. You can’t neglect monitoring and improving the day-to-day activities of the business just because you paid a gazillion dollars to train some people to be expert problem-solvers.

But when you spend a gazillion dollars on problem-solving training, everything begins to look like a problem. You must first make sure that people at all levels of the company are measuring the right things. If they aren’t, your Black Belts will work on achieving objectives and closing gaps that have no relationship to the bottom line. You must examine your product and customer portfolio. If you don’t, your Black Belts will find ways to increase your production rate on products and services that lose money with each unit, and try to make it up in volume.

I also found that Six Sigma started to mean so many things that it meant nothing.

With apologies to the Bard, I come not to widen the definition of Six Sigma, but to narrow it.

For the purposes of this column, an unreasonable approximation of sanity in the Six Sigma sea, let’s call Six Sigma “that component of a business concerned with solving big problems and closing large gaps in performance using the scientific method and the knowledge of process experts.”

I like this definition because it doesn’t deny that there are other components to a business and that Six Sigma isn’t everything you need to run a business. It also limits the scope of Six Sigma to problem-solving, which is what DMAIC (define, measure, analyze, improve, control) is designed to do.

I know, I know. Design for Six Sigma (DFSS) isn’t about closing gaps. One way of looking at DMAIC is as the process to use when you have one metric that’s not where it needs to be—all other metrics associated with the process need only to be maintained. DFSS is what you use when you’re redesigning a process or product and have to optimize across many output metrics. See, I think DFSS is just good design practice and associating it with the term Six Sigma is distracting. In a design cycle you’ll clearly be solving problems, and you could conceivably use design tools in problem solving, so some tools are held in common.

What about the term lean Six Sigma? Well, there’s as much or more to be learned from the Toyota production system as there is from Six Sigma, but I feel combining the two further confuses the issue of what Six Sigma (and, for that matter, lean) is.

There are a bunch of systems, methodologies and tools you need to run a business successfully. One of these methodologies is advanced problem solving, and that is how I see Six Sigma.

This is a very limited scope compared to what some providers (including myself) have claimed. But limiting the scope to problem solving has the advantage of clarifying what to expect, and what not expect, from Six Sigma. It also makes it easier to fit it together with the other elements a business needs, and it makes it obvious that these other elements must be given resources as well. (I wonder if any of you have seen Six Sigma implemented at the expense of these other critical components of your business.) By the way, leave out the finding and selecting of projects from the definition of Six Sigma. Project identification and selection should be driven from strategic planning activities, another topic in itself. This is critical input into Six Sigma, but not part of it.

This doesn’t mean I won’t talk about other topics under the greater Six Sigma rubric. Anything is fair game, my friend. I just think a narrow definition may enhance people’s understanding of what Six Sigma is and what else their business needs to do.